How a three-way catalyst is affected under transient conditions: A study of Pt-Rh/Al2O3 catalyst

Abstract This publication describes results obtained for CO, NO and C 3 H 8 conversion over alumina supported Pt/Rh, Pt and Rh catalysts operating under transient conditions. We show that, for the bimetallic catalyst, oxygen plays an important role in changing the surface composition. By performing activity testing experiments under cycling conditions and different gas mixtures, along with ‘step-change’ experiments, we suggest that, under fuel-rich and stoichiometric conditions, both Pt and Rh exist on the surface in a reduced state. However, under fuel-lean conditions, we show that Rh segregates from the Pt forming an inactive surface oxide, thought to be Rh 2 O 3 . It is shown that this redox process occurs, within 10 seconds.